1. Field of Invention
The present invention relates to a forming method of a laminated structure by internal oxidation, and more generally to a forming method of a laminated structure by internal oxidation to form the above-mentioned laminated structure having oxide layers and metal layers stacked alternately.
2. Description of Related Art
Conventionally, the property of a material or a device and the accuracy and reliability of a product or a reproduction are usually achieved by a surface modification technique. For example, in a press-molding glass technique, a protection film is coated on the surface of a mold base material to extend the lifetime of the mold, thereby reducing the cost of the press-molding glass product. At present, a noble metal is widely applied in the press-molding glass industry due to the advantages of high chemical stability, erosion resistance, high mold-releasing property and high-temperature stability, so as to avoid a reaction or an adhesion from occurring between the mold and the glass, provide enough hardness and mechanical strength to maintain the quality of the mold itself, improve the thermal-shock resistance of the mold, and extend the lifetime of the mold.
However, a protection film of noble metal is required to be removed through a fine processing when it is damaged, and another protection film of noble metal is then coated again for the regeneration purpose. The increased cost for the mold regeneration process almost the same with the cost for manufacturing a new mold. Moreover, removing the damaged protection film of noble metal and coating another protection film of noble metal are time-consuming. Accordingly, the efficiency of the mold regeneration is low. Therefore, a film-stripping regeneration is developed. In details, a buffer layer is coated below a surface protection film, and the film-stripping is done by erosion and controlled by the chemical difference between the surface protection film and the buffer layer, so as to remove the damaged surface protection film. Thereafter, another new surface protection film is coated for the regeneration purpose.
Besides, since the noble metal is expensive, a high-temperature alloy such as a Ta-containing alloy disclosed in U.S. Pat. No. 5,538,528 is used instead. A Mo-containing alloy is also usable, but a Mo—Ru alloy film reacts with glass if not under vacuum. Mo is oxidized more easily in an atmosphere containing 10 ppm oxygen, so that the surfaces of upper and lower molds are roughened to cause the glass adhesion. Therefore, it is necessary to develop a protection film with stable oxide.
Moreover, a diamond film is usually coated on the surface of a cemented carbide mold. When a cobalt-containing cemented carbide mold is used, it is required to avoid cobalt from diffusing out, otherwise diamond nucleation is impossible and a graphite is formed. Accordingly, a barrier layer is coated on the surface of the cemented carbide mold to prevent cobalt from diffusing to the nucleation sites of diamond. However, the conventional barrier layer is a single-layer structure with less barrier ability against cobalt diffusion, so that it is unable to effectively block cobalt from diffusing to the nucleation sites of diamond.